ISOtunes Sport DEFY Slim Tactical Earmuffs 20 NRR Black. Slimmer Fit. DEFY Slim Basic delivers superior protection in a no-frills ultra-slim design. Tactical Sound Control allows you to hear and control ambient sound volumes all while protecting you from harmful gunshot noises. DEFY Slim Basic is the ultimate earmuff for distraction-free high-performance protection. Specifications for ISOtunes Sport DEFY Slim Tactical Earmuffs 20 NRR: Manufacturer: ISOtunes Sport NRR: 20 dB Condition: New Package Contents: ISOtunes Sport DEFY Slim Tactical Earmuffs 20 NRR ISOtunes Sport IT-42: DEFY Slim Tactical Earmuffs Black Small/Large